I am Vinod. I will try my best to help you resolve this issue.
Remove the credit card information from the itunes in your computer. Make sure it says "No credit card on file" under "Payment Information". If you use itunes in any other devices such as ipod/ipad/iphone, sign out of itunes store from those too. Restart all your devices including the computer. Then sign into itunes from the computer and enter the payment information
I removed my information, restarted the computer but it did not work. I selected none under credit cards, but I cannot put it to "no credit card on file" under "payment information" Where is "payment information"?
If you have selected "none" under credit cards, it is enough. Do you have any other devices such as ipod touch/iphone/ipad from which you access the itunes store? If you do, turn off those devices and the computer. Then restart the computer and try to enter the credit card. Then try to buy the song.
Also sign out of itunes store from all those devices before restarting. Also make sure your credit card is within the expiry date and the withdrawal limit is not exceeded.
Or if you have changed your credit card/address in the bank, make sure you update those information in itunes. You can review and edit your account information from http://myinfo.apple.com.
This is still not working. I took my credit card info off of the computer, turned off my phone, restarted everything and added my credit card info again. It still says "there are errors or ommissions" in my billing information but there are none that I can find. All the information is complete and correct. Now what? And is there a phone number I can call?
Sorry to hear that. In this case it is better to contact the Apple tech support 1-800-2752273 or email itunes from www.apple.com/support/itunes